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Under the Clean Air Act, EPA is required to periodically review and, if appropriate, revise the air quality criteria and national ambient air quality standards (NAAQS). On April 18, 2018, the EPA published a final action in which the Agency retained the primary (health-based) NAAQS for oxides of nitrogen without revision. This review includes the preparation of an Integrated Review Plan, an Integrated Science Assessment, and if warranted, a Risk/Exposure Assessment, and also a Policy Assessment by EPA, with opportunities for review by EPA’s Clean Air Scientific Advisory Committee (CASAC), at public meetings, and by the public announced at stakeholder meetings, EPA's website and in the Federal Register. Opportunities for public participation in the development of these assessment include through the offering of comments to the CASAC at public CASAC meetings and directly to the EPA. These assessments inform the Administrator’s proposed decision as to whether to retain or revise the standards. This proposed decision will be published in the Federal Register and announced on EPA's website, with opportunity provided for public participation, such as submission of comments to the rulemaking docket and public hearings. Additionally, opportunity is provided for Tribal consultation. The Administrator’s final decisions will take into consideration the review documents and public comment on the proposed decision. EPA is under a consent decree for this review which includes deadlines to issue a final Integrated Science Assessment no later than September 30, 2026; sign a notice setting forth its proposed decision no later than January 17, 2028; and sign a notice setting forth its final decision no later than November 10, 2028.